BMX Junior

BMX Junior: the size where racing really starts

The Junior class takes riders measuring between 122 and 134 cm, generally aged 7 to 10. This is the size where the child strings motos together, carries speed through the berms and starts jumping. The bike has to keep up on two fronts: reach, to hold the gate position, and braking.

Is it the right size for my child?

Measure barefoot and place the child among the neighbouring sizes:

The Junior band is wide: 12 cm separate the bottom from the top. Under 126 cm, aim at a 17.75" top tube; above 130 cm, an 18.25" leaves a season of margin. Gate test: with elbows slightly bent, the rider should bring the shoulders over the front axle without feeling cramped. Feeling boxed in at 133 cm, compare with our BMX Expert bikes; at 122 cm and starting out, a BMX Mini at the top of its range stays easier to handle.

The numbers on a Junior frame

• Top tube 17.75" to 18.25" depending on brand and model year
• 20" wheels on 451 rims, most often with 20 x 1-3/8" tyres
• Cranks from 145 to 155 mm, adjusted to leg length
• Rim or disc braking depending on the level of the build
• Aluminium frame, steel fork at entry level, carbon on higher builds
• Slim seat post with matching clamp, 22.2 mm handlebar

Rim or disc in Junior?

Both systems genuinely coexist in this size. The V-brake is light, quick to set up and cheap to maintain: it suits a rider discovering racing perfectly. The disc brake brings consistent power in the rain and finer modulation at the lever, a real gain as soon as the child carries speed. A disc does require a frame with a tab, a compatible rear hub and a 140 or 160 mm rotor: it is decided when the bike is bought.

The models available in Junior

Inspyre covers the class with the aluminium Evo Disk, the Evo-C Disk with carbon fork and wheels, and the Concorde for the most complete builds. Chase offers the Edge Junior with a triple-butted 6061-T6 frame and disc brake. Meybo runs the TLNT on rim brakes and the Superclass on disc. Position One holds the entry level on V-brake, Stay Strong the top end on the V5 platform.

Setting the bike to the rider

A correctly sized Junior bike still needs adjusting. Saddle height is set so the leg stays slightly bent at the bottom of the stroke; bar height is changed through headset spacers and handlebar rise. Cranks that are too long break the cadence: on a slight rider, drop 5 mm rather than force it.

Anticipating the move to Expert

Above 134 cm the rider moves into Expert: the same 20" wheel on 451 rims, but a top tube of 18.5" to 19.5" and cranks of 155 to 165 mm. Wheels, saddle, number plate and protective gear all carry over to the next bike.

The BMX RACING advice

Give us the child's height, inside leg and race schedule: we confirm the top tube, the rim-or-disc choice and the crank length before shipping. Every size sits together in the BMX bikes and frames section. Dispatched within 24 to 72 hours, you can spread the cost over 2 or 3 payments.

To place a Junior against the whole range, crank lengths included, read our BMX race sizing guide.